I'm going to be away from home and my Model 3 will sit in the garage unused for about six weeks. My question is whether I should leave it plugged into the Tesla wall charger in my garage or let vampire drain do its thing and then charge it up when I get home. I'm concerned that if I don't leave it on the charger and the charge is completely drained by the time I get home, that there might be a loss of settings or some other problem.
The answer to this question from Tesla's point of view is on page 122 of the manual, which specifically talks about charging.
The short version of that is, plug in the car when you are not driving it. Every time. (thats tesla's direct recommendation). Others sometimes feel differently, but the tesla itself is telling you to plug it in when you are not driving it, ESPECIALLY if you will not drive it for a while.
Here are the quotes from the users manual, which you can download from the tesla website in your account if you have not done so already:
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About the Battery
Model 3 has one of the most sophisticated
battery systems in the world. The most
important way to preserve the Battery is to
LEAVE YOUR VEHICLE PLUGGED IN when
you are not using it.
This is particularly
important if you are not planning to drive
Model 3 for several weeks.
When plugged in,
Model 3 wakes up when needed to
automatically maintain a charge level tha
maximizes the lifetime of the Battery.
Note: When left idle and unplugged, your
vehicle periodically uses energy from the
Battery for system tests and recharging the
12V battery when necessary.
There is no advantage to waiting until the
Battery’s level is low before charging.
In fact,
the Battery performs best when charged
regularly.
Note: If the Model 3 Battery becomes
completely discharged in a situation in which
towing is required, the owner is responsible
for towing expenses. Discharge-related towing
expenses are not covered under the Roadside
Assistance policy